1. Field of the Invention
The present invention relates generally to a process for preparing zirconia ceramic and similar ceramic materials. More particularly, it relates to a process used to metallize the surface of zirconia ceramic and similar ceramic materials, so that the electroless nickel chemistry is distributed evenly on the material's surface.
2. Brief Description of Prior Art
Zirconia ceramic is a high technology ceramic that has high strength and hardness and has excellent surface smoothness that make this material desirable in applications such as pump parts, hip replacement joints, golf cleats, buttons, knife and scissor blades, metal extrusion dies, electronic components such as duplexer filters, and in other applications where similar conditions exist. In addition, it is often desirable with some applications to have the surface of the zirconia ceramic metallized to provide enhanced electrical or mechanical requirements. The very qualities that make zirconia ceramic material desirable for use in these applications as described also makes it a difficult material to metallize with plating technology.
Traditional electroless plating technology includes an “etch” process, where highly active acids such as hydrofluoric acid is used to etch the surface of the material so that the material will retain the “surface activation” in subsequent steps. Activating the surface of the material requires seeding the surface of the material with metal ions that will then exchange with the electroless nickel chemistry (in subsequent steps) as part of an autocatalytic process that distributes nickel evenly on the material's surface.
Activation may be accomplished with such known processes as “tin sensitizer” followed by a rinse, followed by a “palladium activator” followed by a rinse.
In known plating processes, each chemistry step is traditionally followed by a rinse step to avoid mixing of chemistry that can cause contamination of the subject chemicals. Such contamination may likely result in the chemistry not functioning to expected specification. Non-zirconia ceramic is much more porous and not as hard as zirconia ceramic. Such porous surface of non-zirconia ceramics allows the palladium activator or other activation chemistry to be retained on the surface after rinsing. That is not the case with zirconia ceramics.
Traditional plating techniques known in the art will not work on zirconia ceramic. As described, zirconia ceramic is a high technology ceramic that has high strength and hardness and has excellent surface smoothness. As a result, acid etch chemistries known in the art do not penetrate the surface of the zirconia ceramic material due to its hardness, and the subsequent activation chemistry has weak adhesion to the material's surface due to the smoothness of the surface. Upon rinsing following activating the surface as described above, the activation chemistry is removed from the surface of the material and subsequent electroless nickel plating is inconsistent.
To the best knowledge of the applicant, a suitable, commercially practicable method has not been found for the preparation of zirconia ceramic material for electroless nickel plating, so that the electroless nickel chemistry is distributed evenly on the material's surface.
As will be seen from the subsequent description, the preferred embodiments of the present invention overcome shortcomings of the prior art.